This application claims the benefit of Provisional Application No. 60/672,030 filed on Apr. 18, 2005. The disclosure of this provisional application is incorporated by reference as though set forth at length.
This invention relates to mixing and concomitant delivery of temporarily flowable solid materials at a use site. More specifically, this invention relates to mixing and delivery mixtures of concrete sand casting compositions, plates of paris compositions and the like.
There are a number of solutions to the problem of mixing and dispensing concrete; some of these demand use of heavy equipment while others use more specialized equipment and a number of personnel to operate the equipment. Other solutions involve lighter weight equipment or even portable equipment; yet much of the history of concrete making and placement on a small scale is characterized by the manual work of lifting, loading, mixing and manually hauling.
Complications revolve around mixing techniques including the need to control relative proportions of cement, sand and gravel and other additives. Substantial work has been completed in attempts to automate or mechanize proportioning of the ingredients. The need, of course, is to provide an end product that meets various building and construction code specifications. Moreover, there is general recognition within the community of those skilled in the art of handling that minimal handling or mixing of the hydrated concrete mixture is preferred prior to placement.
The use of dry premixed ingredients provides guaranteed proportions of the essential components without the end user having to be concerned about mixing proportions; further if the end user pre-mixes the dry components in a separate batch-type process rather than metering the ingredients in a continuous process the simplicity and reliability of the proportions is more readily achieved. Of course, it does not matter whether the end user actually performs the proportioning so long as the end user has assurance that a mix conforms to specified proportions.
As recommended by the Portland Concrete Association, the delivery and placement of a hydrated mixture should be performed with minimal handling and re-mixing once the initial hydrated mixture is created. Accordingly, both speed of placement and minimal handling are desirable features. Accordingly, facile handling with minimal personnel and minimal capital outlay for equipment is a desirable objective within the community of mixing and delivering concrete.
One prior arrangement comprises a wheeled concrete mixing device which incorporates a hopper mounted above a trailer frame. The trailer frame is linearly movable on track elements and delivers its contents to a conveyor belt located below the hopper. Here a two-hopper system is used and the second hopper feeds the flowable material to a screw conveyor. The second hopper in this system is rigidly mounted and fixed in relation to the trailer frame.
Another particulate mixer uses multiple hoppers fixed on a frame and the hopper support frame is also fixed in relation to a vehicle transport frame. In this system a set of feeding augers each driven by a separate hydraulic motor delivers contents to a final delivery auger. The final delivery auger is angularly fixed in relationship to the intermediate delivery augers during operation. Further the delivery auger is fixed in relationship to the ground because the final delivery auger exits to the side of the trailer frame.
Still another mixer uses a fully encased cover over a mixing and conveying auger and which uses the encasing cover as a structural frame support for the wheels, a towing hitch, a drive engine and a delivery hopper. An internal combustion engine driving the auger is located on the distal end of the auger assembly thus necessitating the placement of transport wheels near the distal end. This arrangement severely limits the adjustment of the delivery height of the distal or delivery end of mixing system and access to the auger chamber.